Environmental changes in biodiversity hotspot ecosystems of
South Ecuador: RESPonse and feedback effECTs (FOR2730)

Abstract:

The influence of herbivores on plants in tropical forests is enormous. Leaf area loss through herbivory may alter biochemics, physiology and morphology of a plant and thus have a negative influence on the plant‘s fitness. Hence, herbivory is a selective factor for the species composition of plant communities. As a result of the progressive industrialisation on earth an increase in the input of atmospheric nitrogen (N) and phosphorus (P) is expected. Against this background, in this study the influence of N and/ or P fertilization on the herbivory in a tropical montane forest of southern Ecuador was investigated. Here, in a nutrient manipulation experiment (NUMEX), study areas are fertilized with low amounts of N (50 kg/ha/year), P (10 kg/ha/year) as well as N+P (50 kg/ha/year and 10 kg/ha/year respectively). Herbivory was quantified by one-time-measurements of absolute leaf mass loss and percentaged leaf area loss of the four most common tree species of the study area (Alchornea grandiflora, Graffenrieda emarginata, Hieronyma moriztiana, Myrcia sp.) and a sample of randomly chosen trees representing the community. It was investigated whether possibly changed herbivory rates result from increased nutrient concentrations in the leaves or an altered specific leaf area (SLA). The community lost marginally significantly (p<0.1) more leaf area on N fertilized areas than on control areas and herbivory rates were significantly (p<0.05) higher on N fertilized for three of the four species. Combined N+P fertilization had a significant (p<0.05) increasing effect on the herbivory suffered of two species. P fertilization did not show any effect on herbivory. The increased herbivory rates on three of the four most common species with increasing N availability may lead to a decreasing competitive strength of these species in the future and thus to less appearence in the community. Regarding the nutrient content and morphology of the leaves, the most striking feature was a high species-specific variability in the reaction to the different treatments. There was no influence of the different fertilizations on foliar nutrient content or morphology of the community. In one of the four species a connection between increased leaf area loss and elevated leaf N content was found on N fertilized areas. There was no evidence, that increased SLA results in increased herbivory rates. It is to suggest, that within species other parameters, e. g. altered leaf toughness or content of secondary metabolites may exert a stronger influence on the variability of herbivory rates with differing N availability. In conclusion, the study showed that in a tropical montane forest of southern Ecuador soil nitrogen availability had an increasing effect on feeding performance of herbivores.

Abstract:

This study aims to determine trends in a long-term monthly mean series of element concentrations and water and element fluxes with incident precipitation, throughfall, stemflow and dry deposition, using a nonparametric method (the Mann-Kendall trend test). Calculated were both the seasonal and the non-seasonal Mann-Kendall trend test, a robust estimate of the slope is determined for all detected trends as Kendall-Theil Robust Line (KTR-Line). The equipment in the study area was installed on three transects, about 20 m long with an altitude range of 10 m, at 1900 - 2010 m a.s.l.. Incident rainfall, throughfall and stemflow were measured weekly by recording single volumes for each collector between March 1998 and April 2008. The concentrations and element fluxes (including canopy budget) of Ca, Mg, Na, K, Cl-, NH4+-N, NO3--N, dissolved organic nitrogen (DON), total dissolved N (TDN), PO43--P and total dissolved P (TDP) were determined. The water fluxes showed a significant increasing trend in incident rainfall and stemflow. Comparing the numbers of trends, there is an increasing from incident rainfall > stemflow > throughfall > dry deposition > canopy budget. The concentrations of base metals showed significant decreasing in incident rainfall. An increasing in the concentrations of nitrogen as well as phosphorous was also found in incident rainfall. Throughfall showed a significant increasing H + concentration, as well as a decreasing Mg and Na concentration. In stemflow the concentration of nitrogen and phosphorous decreased extremely (p < 0.001) significant, while there was a significant increasing concentration of K and Mg. There is a significant decreasing in the element fluxes of base metals in incident rainfall that is ongoing in throughfall, resembling the trends in the concentrations. In stemflow are significant increasing trends in K and Mg. The trends in the element flux of nitrogen and phosphorous are similar to those of the concentrations, significantly increasing in incident rainfall, with an increasing flux of phosphorous in throughfall and an (extremely) increasing flux of nitrogen in stemflow. The dry deposition of H+ showed a significantly increasing, as well as the dry deposition of nitrogen and phosphorous. There is a significant decreasing in the dry deposition of Ca. The canopy budget showed a decreasing trend for H+ and nitrogen.

Abstract:

Gegenwärtige anthropogene Umweltveränderungen verursachen einen fortschreitenden Verlust an Biodiversität. Der Verlust von einzelnen Arten durch Habitatveränderung, Klimawandel und das Einwandern von invasiven Arten wurde intensiv untersucht. Jedoch sind die Auswirkungen von Arten Interaktionen nur unzureichend erforscht. Da der Mensch schnelle Umweltveränderungen hervorruft, ist es wichtig zu verstehen, welche Konsequenzen diese in der biotischen und abiotischen Umwelt, in Populationsstrukturen und in koevolutionären Prozessen haben (Leimu et al. 2012). Eine wichtige ökologische Interaktion ist dabei die Koevolution zwischen Pflanzen und Herbivoren (Coley & Barone 1996). Wechselwirkungen zwischen Pflanzen und Herbivoren sind mit die dominantesten in der Natur (Carmona et al. 2011). Innerhalb verschiedener Ökosysteme gibt es Unterschiede in den Herbivorieraten (Cyr & Pace 1993). Besonders in tropischen Wäldern ist Herbivorie ein zentraler Prozess (Dirzo & Boege 2008). Im Durchschnitt wird in tropischen Regenwäldern jährlich 11 % der Blattfläche durch Herbivore gefressen (Coley & Barone 1996). Pflanzen haben eine Vielzahl von Abwehrmechanismen entwickelt, die den Einfluss von Herbivoren reduzieren. Dazu gehören unter anderem chemische, mechanische und phänologische Abwehrmechanismen. Herbivore auf der anderen Seite haben Mechanismen entwickelt, um solche Abwehrstrategien zu umgehen. Dieses Wechselspiel beeinflusst Nahrungsnetze, Diversität von Artengemeinschaften sowie Nährstoffkreisläufe und somit alle Organismen im tropischen Wald (Coley & Barone 1996). Für sehr viele vertebrate und invertebrate Herbivore, sowie Pathogene, bilden Blätter eine entscheidende Nahrungsquelle. Die wichtigste Gruppe bilden die folivoren Insekten. Sie sind eine taxonomisch und morphologisch hoch diverse Gruppe und die wichtigsten Konsumenten in tropischen Wäldern (Coley & Barone 1996). Coley und Barone schätzen den Beitrag kauender Insekten an der jährlichen Herbivorie in tropischen Wäldern auf mindestens 75 %. Kauende Insekten sind sehr wirtsspezifisch und haben ein enges Nahrungsspektrum. Demnach entsteht ein größerer Anteil der Schäden durch spezialisierte Herbivore als durch Generalisten (Barone 1998). Coley & Barone schließen daraus, dass spezialisierte Insektenherbivore auch für die Ausbildung von pflanzlichen Abwehrmechanismen eine größere Rolle spielen.

Abstract:

Mit der Meereshöhe und der Topographie verändern sich klimatische Faktoren und Bodeneigenschaften. Damit einher gehen Veränderungen der Blattmorphologie, der Blattnährstoffgehalte und der Limitierung der Vegetation durch bestimmte Nährstoffe. In dieser Studie werden jene Zusammenhänge entlang eines Höhengradienten (1000, 2000 und 3000 m ü.M.) und an jeweils drei topographischen Lagen (Unter-, Mittel- und Oberhang) in südecuadorianischen Bergregenwäldern untersucht. Dazu wurden die mittlere Blattfläche, die spezifische Blattfläche sowie die Blattgehalte von N, P, K und Ca analysiert und verglichen. Die mittlere und die spezifische Blattfläche nahmen mit zunehmender Meereshöhe und der Topographie, vom Unterhang zum Oberhang, tendenziell bis signifikant ab. Ähnliche Resultate ergaben sich bei den Blattnährstoffgehalten, wobei der Trend hier nicht ganz eindeutig ist. Zudem wurden die Bodenparameter organische Auflage, pH-Wert, Stickstoffmineralisation, verfügbarer Phosphor und C/N-Verhältnis gegen die blattmorphologischen Daten sowie die N und P-Gehalte der Blätter aufgetragen. Mit zunehmen-der Meereshöhe und mit der Topographie vom Unterhang zum Oberhang nehmen die Bodennährstoffgehalte ab; ebenso sinkt der pH-Wert; die Mächtigkeit der organischen Auflage und das C/N-Verhältnis des Bodens nehmen zu. Zwischen den Bodenparametern und den Blatteigenschaften wurden enge Korrelationen gefunden, die auf ein Netzwerk gegenseitiger Beeinflussung der einzelnen Faktoren hinweisen. Des Weiteren kann im gesamten Untersuchungsgebiet auf Grund eines sehr hohen N/P-Verhältnisses von einer stärkeren Limitierung der Vegetation durch Phosphor als durch Stickstoff ausgegangen werden.

Abstract:

Wood specifc gravity (WSG) is a key plant functional trait and an important variable for aboveground tree biomass (AGB) and carbon stock estimation. Knowledge about spatial patterns of WSG and its environmental constraints in tropical mountain forests is comparatively scarce, especially when it comes to the effects of elevation and topography. Moreover, the answer to the question whether gradients in WSG in uence spatial patterns of AGB remains uncertain. In this study, altitudinal and topographical gradients in AGB and WSG were assessed in a tropical mountain forest ecosystem in southern Ecuador. For this purpose, a total of 1769 trees in 54 permanent sample plots along environmental gradients were censused and WSG was measured using a Pilodyn 6J wood tester. The obtained data were used to estimate AGB using allometric models from Chave et al. (2005) both with and without tree height as a predictive variable. WSG was found to increase signifcantly upslope by an average of 9,3 %, but did not show altitudinal gradients. If computed with tree height, AGB decreased signi cantly both upslope and with elevation. AGB on lower slopes in the average was 95,8 % bigger than on upper slopes and decreased more than 1.5-fold with increasing altitude from a mean of 288.9 t ha-1 at approx. 1000 m a.s.l. to 112.3 t ha-1 at approx. 3000 m a.s.l.. If computed without tree height, AGB was found to be lowest at intermediate elevations, and AGB results were systematically higher. A possible explanation for the upslope decrease in WSG are reduced growth rates induced by nutrient limitation. The reason for the gradients in AGB is most likely the altitudinal and upslope decrease in tree height in the study area which in former studies has been related to nutrient limitation as well. Given the enormous altitudinal decrease of tree height in tropical mountain forests, performance of allometric models which do not use tree height as a predictive variable was found to be poor. The observed gradients in WSG could not predict the patterns in AGB, in contrast, AGB was found to be highest in sites with low WSG.

Abstract:

Tropische Bergwälder zeichnen sich durch steile Hanglagen sowie sich verschlechternde Wachstumsbedingungen mit zunehmender Meereshöhe aus. Letzteres ist auf einen verringerten Nährstoffzyklus bzw. eine geringere Nährstoffverfügbarkeit aufgrund niedriger Temperaturen und vernässter, sauerstoffarmer, saurer Böden in höheren Lagen zurückzuführen (TANNER et al., 1998; SCHRUMPF et al., 2001; SCHUUR, 2001; BENNER et al., 2010; HERTEL & LEUSCHNER, 2010). Vor allem im oberen tropischen Bergwald wurde ein hohes C/N-Verhältnis in der organischen Auflage sowie eine reduzierte Abbau und Mineralisationsrate festgestellt (TANNER et al., 1998; BENNER et al., 2010). Zudem nimmt die oberirdische Biomasse mit steigender Höhe ab, was unter anderem mit einer Verschiebung der Kohlenstoffallokation von oberirdischen zu unterirdischen Pflanzenstrukturen erklärt wird (LEUSCHNER et al., 2007; MOSER et al., 2008). Eine geringe Nährstoffverfügbarkeit aber auch eine ungünstige Luftversorgung im Boden führen dazu, dass die Pflanzen mehr Kohlenstoff in das (Fein-) Wurzelsystem investieren (BROUWER, 1983; LÕHMUS et al., 1989; OSTONEN et al., 2005), um eine ausreichende Nährstoffversorgung zu gewährleisten (LEUSCHNER et al., 2007; GRAEFE et al., 2010; HERTEL & LEUSCHNER, 2010). Nicht nur die Meereshöhe, sondern auch die Hanglage, also die Topographie, spielt in tropischen Bergwäldern eine große Rolle. So hat die topographische Hanglage nicht nur Einfluss auf die Habitatdiversität (HOMEIER et al., 2010) sondern auch auf die Wasser und Nährstoffverfügbarkeit im Boden (KUBOTA et al., 1998; DAWS et al., 2002; TSUI et al., 2004). Feinwurzeln – im Allgemeinen definiert als Wurzeln mit einem Durchmesser < 2 mm – sind hochdynamische und wichtige Pflanzenorgane, die für die Wasser und Nährstoffaufnahme zuständig sind. Trotz ihres geringen Anteils an der Gesamtbiomasse eines Baumes verbrauchen unter anderem die Produktion, der Umsatz und das Wachstum der Feinwurzeln große Mengen Kohlenhydrate (VOGT et al., 1996). Nach LEUSCHNER et al. (2004) werden die Kosten der Pflanze für die Bildung und Erhaltung von (Fein-) Wurzeln durch das Ausmaß der Kohlenstoff und Nährstoffsenke bestimmt. Die Höhe der Nährstoff und Wasseraufnahme stellt hingegen den Nutzen dar, welchen die Pflanzen aus den (Fein-) Wurzeln ziehen (LEUSCHNER et al., 2004). Neben der Lebensdauer der (Fein-) Wurzeln (EISSENSTAT & YANAI, 1997) ist die (Fein-) Wurzelmorphologie ein entscheidender Faktor hinsichtlich des Kosten/Nutzen-Verhältnisses (LEUSCHNER et al., 2004). Das Feinwurzelsystem und dessen Dynamik wurden vor allem in temperaten und borealen Wäldern untersucht (VOGT et al., 1996; CAIRNS et al., 1997; GILL & JACKSON, 2000). Im Vergleich dazu wurden trotz der Bedeutung tropischer Wälder im Hinblick auf den globalen Kohlenstoffhaushalt (MALHI et al., 1999; POST & KWON, 2000) bislang nur wenige Studien über die Struktur und Funktion des Feinwurzelsystems in diesen Ökosystemen durchgeführt. Vorliegende wurzelökologische Studien wurden außerdem vorwiegend in tropischen Tieflandwäldern durchgeführt (u.a. CUEVAS & MEDINA, 1988; GREEN et al., 2005; SILVER et al., 2005; TRUMBORE et al., 2006), während es zum Feinwurzelsystem in tropischen Bergwäldern nur vereinzelte Studien gibt (CAVELIER, 1996; KITAYAMA & AIBA, 2002; HERTEL et al., 2003; HERTEL & WESCHE, 2008; Girardin et al., 2010). Vor allem zum Einfluss der topographischen Hanglage auf das Feinwurzelsystem wurden bislang noch keine Studien durchgeführt. Deshalb ist bisher nur wenig über die Anpassungsmechanismen des Feinwurzelsystems an die Bedingungen tropisch montaner Wälder bekannt (HERTEL & LEUSCHNER, 2010). Die vorliegende Studie über den Einfluss von Meereshöhe und Topographie auf Biomasse und Morphologie von Feinwurzeln in Bergwäldern wurde im Zuge des DFGForschergruppenprojekts 816 („Biodiversität und nachhaltiges Management eines megadiversen Bergwald-Ökosystems in Südecuador“; http://www.tropicalmountainforest.org) in Südecuador durchgeführt. Auf insgesamt 54 Flächen in 1000, 2000 und 3000 m Meereshöhe und in unterschiedlichen topographischen Hanglagen wurde die Feinwurzelmasse, -dichte und -morphologie untersucht. Dabei sollten die folgenden Fragestellungen analysiert werden: 1) Welchen Einfluss hat die Meereshöhe auf die Masse, Dichte und Morphologie der Feinwurzeln? 2) Welchen Effekt hat die topographische Hanglage auf die Masse, Dichte und Morphologie der Feinwurzeln? 3) Welche Unterschiede bzw. Gemeinsamkeiten haben Meereshöhenund Topographieeffekt auf die oben genannten Parameter des Feinwurzelsystems?

Abstract:

The impact of human actions on the environment is enormous. Due to a continuous increase in population and the growing industrialization of a globalized world man’s influence on the dynamic of ecosystems and biospheres is steadily expanding. As a result of these augmenting human activities, an increase in the input of atmospheric nitrogen (N) and phosphorus (P) is expected. In a field study in a tropical mountain rain forest in southern Ecuador – an area assumed to be limited in N – permanent plots are fertilized with low amounts of N (50kg/ha/year), P (10kg/ha/year) as well as N and P (50kg/ha/year and 10 kg/ha/year respectively), thereby simulating higher nutritional dispositions in the respective plots. Because varying nutritional dispositions have the greatest effect on seedlings, this thesis’ aim is to examine to what extent applications of N and P can influence the growth and abundance of seedlings, thus affecting the tree regeneration in tropical montane forests. A total of 626 plants between 5 and 150 cm in height have been measured. Among the most common families were Rubiaceae, Melastomataceae, Myrtaceae, Arecaceae and Euphorbiaceae. The most commonly encountered tree species were Graffenrieda emarginata Triana (Melastomataceae) and Myrcia spec. nov. (Myrtaceae). Considering the total number of measured seedlings, N in general seems to have a positive effect on tree regeneration. A generally increased growth in height and stem diameter on the Nand NP-plots proves that N is a limiting factor in this mountain rain forest. Additions of P, on the contrary, do not show any effects on the plants, wherefore P does not seem to be a controlling factor for tree regeneration in this tropical mountain rain forest. However, fertilization of N does not have a positive effect in growth on every family. Whereas the Euphorbiaceae and Melastomataceae families were able to increase their growth on Nand NP-plots, Arecaceae only show positive effects on NP-plots. Altogether without any gain from N-additions seem to be the Myrtaceae and Rubiaceae families. Moreover, the tree density of Rubiaceae was even significantly reduced on Nand NP-plots. Especially an increased leaf area loss on the Nand NP-plots presents an elevated risk for plant families such as Myrtaceae and Rubiaceae, because they do not seem to have the ability to compensate the increased leaf area loss by an augmented growth rate. However, a higher appearance and growth of Euphorbiaceae and Melastomataceae due to an increased nutritional input is to be expected in the future. In the long term this development might cause the extinction of their current habitat of the Myrtaceae and the Rubiaceae families, the latter being the currently most widely spread family. As a consequence, it is to be expected that G. emarginata will increasingly emerge as the dominant species, whereas Myrcia spec. nov. will probably play a minor role. Obviously the various tree species have a different need for N, which causes diverse thresholds in N-tolerance.

Abstract:

The thermal structure of a megadiverse mountain ecosystem in southern Ecuador is examined on the basis of temperature measurements inside the natural mountain forest and at open sites along an altitudinal gradient from 1700m to 3200m. The data is used to calculated maps of monthly average minimum, mean and maximum 2m air temperature for the period 1999-2007, needed by ecological projects. The maps are generated by combining the straightforward detrending technique by using a Digital Elevation Model and satellite-based land cover classification. The results reveal a clear thermal differentiation over the year, partly triggered by the change of synoptic weather situation but also by land cover effects. Thermal amplitudes are particularly low during the main rainy season when cloudiness and air humidity are high but markedly pronounced in the relative dry season when daily irradiance and outgoing nocturnal radiation causes distinct differences between the land cover units. Particularly the lower pasture areas gained by slash and burn of the natural forest exhibit the most extreme thermal conditions while the atmosphere inside the mountain forest is slightly cooler due to the regulating effects of the dense vegetation. Thus, clearing the forest clearly reduces the thermal regulation function (regulating ecosystem services) of the ecosystem which might become problematic under future global warming.

Abstract:

Forest-to-pasture conversion has been reported to increase soil organic matter (SOM) in mineral topsoils in the tropical mountain rainforest region of south Ecuador, with subsequent decreases following pasture abandonment. Until now the mechanisms behind these changes have not been fully understood. To elucidate their varied preservation patterns, we analysed root- and shoot-derived organic matter and assessed their contribution to the formation of SOM in topsoils (0?5 cm) on a chronosequence of pastures (Setaria sphacelata (Schumach.); C4) established after slash and burn of the natural forest (diverse C3 plant species) and an abandoned pasture site invaded by bracken fern (Pteridium arachnoideum (Kaulf.) Maxon.; C3). Cutin and suberin biomarkers of the two plant species (grass and bracken) and of forest litter were identified after saponification and their contribution to SOM was studied by compound-specific stable carbon isotope analyses. Our results showed specific root and shoot biomarkers for the two plant species and for forest litter, which often did not correspond to the classification of root-versus shoot-specific monomers reported in the literature. This illustrates the importance of direct biomarker determination rather than using results from studies with different plants. Shoot- as well as root-derived OM of forest and grass origin contributed to the stable SOM pool with decadal turnover times. Forest-derived monomers contributed more to the stable SOM pool compared with grass-derived monomers. &#969;-hydroxy carboxylic acids and &#945;,&#969;-alkanedioic acids of forest origin may have been stabilized in these tropical soils by bonding to soil minerals. Rapid degradation of grass-derived lipids from the same compound classes suggests a saturation of the mineral binding capacity. In pasture soils, the accumulation of SOM was mainly driven by large inputs of root OM. The accumulated SOM during pasture use is, however, lost rapidly after abandonment.

Abstract:

The dependence of aboveground biomass and productivity of tropical forests on soil fertility is not fully understood, since previous studies yielded contrasting results. Here, we quantify aboveground biomass (AGB) and stem wood production, and examine the impact of soil chemistry on these parameters in mature tropical forest stands of the equatorial Andes in Ecuador. In 80 plots of 0.04 ha at four elevation levels (500, 1,000, 1,500 and 2,000 m a.s.l., total sample area = 3.2 ha), we measured ten important soil chemical parameters, inventoried all trees ¸10 cm dbh and monitored stem diameter growth with dendrometer tapes in 32 plots. Top canopy height and stem density signiWcantly decreased from 500 to 2,000 m, while tree basal area increased and AGB remained invariant (344 § 17 Mg DM ha¡1, mean § SE) with elevation. Wood speciWc gravity (WSG) showed a signiWcant, but small, decrease. Stem wood production decreased from 4.5 to 3.2 Mg DM ha¡1 year¡1 along the transect, indicating a higher biomass turnover at lower elevations. The only soil variable that covaried with AGB was exchangeable K in the topsoil. WSG increased with decreases in N mineralisation rate, soil pH and extractable Ca and P concentrations. Structural equation modelling (SEM) revealed that nitrogen availability acts on stem wood production only indirectly through a negative relation between N mineralisation rate and WSG, and a positive eVect of a lowered WSG on stem growth. The SEM analysis showed neither direct nor indirect eVects of resin-extractable P on wood production, but a negative P inXuence on AGB. We conclude that nitrogen availability signiWcantly inXuences productivity in these Andean forests, but both N and P are aVecting wood production mainly indirectly through alterations in WSG and stem density; the growth-promoting eVect of N is apparently larger than that of P.

Abstract:

In tropical mountains, trees are the dominant life form from sea level to above 4,000-m altitude under highly variable thermal conditions (range of mean annual temperatures: <8 to >28C). How light-saturated net photosynthesis of tropical trees adapts to variation in temperature, atmospheric CO2 concentration, and further environmental factors, that change along elevation gradients, is not precisely known. With gas exchange measurements in mature trees, we determined light-saturated net photosynthesis at ambient temperature (T) and [CO2] (Asat) of 40 tree species from 21 families in tropical mountain forests at 1000-, 2000-, and 3000-m elevation in southern Ecuador. We tested the hypothesis that stand-level averages of Asat and leaf dark respiration (RD) per leaf area remain constant with elevation. Standlevel means of Asat were 8.8, 11.3, and 7.2 lmol CO2 m-2 s-1; those of RD 0.8, 0.6, and 0.7 lmol CO2 m-2 s-1 at 1000-, 2000-, and 3000-m elevation, respectively, with no significant altitudinal trend. We obtained coefficients of among-species variation in Asat and RD of 20?53% (n = 10?16 tree species per stand). Examining our data in the context of a pan-tropical Asat data base for mature tropical trees (c. 170 species from 18 sites at variable elevation) revealed that area-based Asat decreases in tropical mountains by, on average, 1.3 lmol CO2 m-2 s-1 per km altitude increase (or by 0.2 lmol CO2 m-2 s-1 per K temperature decrease). The Asat decrease occurred despite an increase in leaf mass per area with altitude. Local geological and soil fertility conditions and related foliar N and P concentrations considerably influenced the altitudinal Asat patterns. We conclude that elevation is an important influencing factor of the photosynthetic activity of tropical trees. Lowered Asat together with a reduced stand leaf area decrease canopy C gain with elevation in tropical mountains.

Abstract:

The moth genus Eois Hu¨ bner (Lepidoptera: Geometridae: Larentiinae) comprises 254 validly described species, 211 of them (83%) occurring in the Neotropical region, 12% in the Asian-Australian region, and 5% in Africa. A checklist of Neotropical Eois is provided and some taxonomic changes are made. Aplogompha noctilaria (Schaus) is excluded from the genus, and Eois bermellada (Dognin) and Eois fragilis (Warren) are transferred to the genus. Further changes include Eois cellulata (Prout) stat. rev., Eois ambarilla (Dognin) stat. rev., and Eois telegraphica Prout stat. rev. By far, the majority of Eois species (82%) were described between 1891 and 1920; approximately half of all species by just two authors. Within the Neotropical region, the majority of species (55%) were described from the tropical Andes (Colombia, Ecuador, Peru, and Bolivia), followed by Central America and the Caribbean (28%), and the rest of South America (17%). Large regions such as the Amazon basin, eastern South America, but also northern Peru are heavily underrepresented. Regional diversity studies provide evidence that the wet tropical Andes are the diversity hotspot of Eois. From a forested elevational gradient (1,020Ð2,670 m above sea level) in southeastern Ecuador, 154 morphospecies are currently known, with only 12% of them described. Regional species richness in Central America is lower (Costa Rica, 66 observed morphospecies along a gradient from 40 to 2,730 m; 29% described). Total richness of the genus is estimated to be 1,000 species in the Neotropical region. If the low proportions of described species only partly recur in other groups of Neotropical geometrid moths, their number may exceed 19,000 species. A taxonomic revision of Eois will be a prerequisite for comparison of ecological data from different regions.

Abstract:

Caterpillar ensembles were sampled on 16 species of shrubs from the family Asteraceae and the genus Piper (Piperaceae) in open and forest habitats in the Andean montane forest zone of southern Ecuador between August 2007 and May 2009. Trophic affiliations of caterpillars to the host plants were confirmed in feeding trials. Overall, species richness of herbivorous caterpillars was high (191 species across all plants), but varied strongly between ensembles associated with different plant species (2–96 lepidopteran species per shrub species). Ensembles on Piper species were characterized by low effective species numbers and high dominance of one or two species of the Geometridae genus Eois Hübner. Low species number and high dominance were also found on latex-bearing Erato polymnioides, whereas ensembles on two other Asteraceae species were far more diverse and less strongly shaped by a few dominant species. The observed diversity patterns fit well to the concept that anti-herbivore defenses of plants are the major factors regulating associated insect ensembles. Local abundance and geographic range of host plants appear to have less influence. Lepidopteran species feeding on Asteraceae were found to be more generalistic than those feeding on Piper species. We conclude that caterpillar ensembles on most, but not all, studied plant species are defined by a small number of dominant species, which usually are narrow host specialists. This pattern was more distinct on Piper shrubs in forest understory, whereas Asteraceae in disturbed habitats had more open caterpillar ensembles.

Abstract:

While many studies analyse patterns of tropical land management with a backward-oriented approach that utilises data of the past, we propose to consider future-oriented modelling approaches to find sustainable land-use options. This proposal is illustrated with application examples for advanced growth modelling in tropical forests, a short overview on financial performance analyses for tropical land uses, and the introduction of a newmodelling approach. Thismodelling approach sees tropical land management as a financial portfolio of land-use options. Its advantage is the ability to make transparent effects of financial risk reduction that arise from mixing forestry and agriculture-based land-use options. The approach thus does not analyse land uses as stand-alone options, like most other analyses do. The land-use portfolio modelling shows that sustainable land use may also be financially attractive for farmers, if abandoned farm lands are reforested (with a native tree species in our case) and sustainable management in natural forests is carried out. We conclude that the combination of advanced growth with sound financial modelling may lead to improved bioeconomic models. Developed bioeconomic models are necessary to increase the biological realism and acceptability of the results obtained.

Abstract:

We usually have only limited knowledge about the economic consequences of land-use decisions, thus they are uncertain. We analyze the implications of this uncertainty on conservation payments (CP) to preserve wildlife-friendly shade coffee production in southwest Ecuador, when conversion to maize is the most profitable alternative. Our objective is twofold: First, we analyze the consequences of applying Stochastic Dominance (SD) to derive CP, an approach making only minimal assumptions about the preferences of farmers. Second, we investigate the effects of land-use diversification to reduce CP by allowing for shade coffee on part of a landholding, and maize production on what remains. CP derived by SD turned out to be at least twice the amount calculated by an alternative method which maximizes a concave utility function?US$ 166 to US$ 294 ha-1 year-1 instead of US$ 86 ha-1 year-1. Given this result, we doubt that the assumptions underlying SD are reasonable for farmers, who are known to be riskaverse. Allowing for land-use diversification has a significant impact on CP. The optimal portfolio share of shade coffee is 27 % and for maize 73 % for moderately risk-averse farmers?without any CP. A larger share of shade coffee is preferable for strongly risk-averse farmers?51 and 49 % maize. The amount of CP necessary to encourage the expansion of shade coffee to 75 %is US$ 40 ha-1 year-1 (for moderately risk-averse) and US$ 19 ha-1 year-1 (for strongly risk-averse farmers). Stimulating diversification may thus help to significantly reduce CP necessary to preserve less profitable agroforestry options.

Abstract:

Tropical mountain forest in the Andes of southeastern Ecuador is regularly destroyed to gain pasture land by cultivating the C4 grass Setaria sphacelata. After recurrent burning of the pastures, the grass is partly outcompeted by the C3 southern bracken (Pteridium arachnoideum). This competition represents the problematic of pasture degradation and increasing deforestation, due to the necessity of new pasture land. Because no information on the growth potential of both species in the Andes of Ecuador is available, a growth simulation model has been improved and properly parameterized with field observations. The measured speciesand site-specific physiological and edaphic parameters are presented in this paper, as well as the model validation with field observations of leaf CO2 assimilation. The validation showed deviations of simulated from observed leaf net assimilation lower than 5% of the observed values. The validated model was run with a fully realistic meteorological forcing of the year 2008 (10 min time step). The main result points to slightly higher growth potential of Setaria with 5879 g m-2 a-1, based on an annual CO2 net assimilation rate of 217 mol CO2m-2 a-1. The calculated growth potential of bracken was 5554 g m-2 a-1, based on the CO2 net assimilation of 197 mol CO2m-2 a-1. In addition, it was shown that decreasing incoming solar radiation and low temperature are favourable weather conditions for bracken in contrary to the pasture grass Setaria.

Abstract:

Tropical mountainous cloud forests belong to the most diverse ecosystems on earth. If you ask scientists which features characterize these ecosystems, then the answers are as diverse as is the flora and fauna within them: persistent cloud cover, reduced solar radiation due to cloud cover, distinctly structured vegetation forms, suppressed evapotranspiration as a consequence of high relative humidity, stripping of clouds by tree canopies and resulting large amount of throughfall, reduced canopy heights, high rainfall rates, gnarled tree trunks at increasing altitudes, substantial epiphyte biomass, moss-covered stems, organic rich and typically wet soils, and – last but not least – extremely high biodiversity with a paramount endemism (Bruijnzeel et al., 2011).

Abstract:

Landslides are a hazard for humans and artificial structures. From an ecological point of view, they represent an important ecosystem disturbance, especially in tropical montane forests. Here, shallow translational landslides are a frequent natural phenomenon and one local determinant of high levels of biodiversity. In this paper, we apply weighted ensembles of advanced phenomenological models from statistics and machine learning to analyze the driving factors of natural landslides in a tropical montane forest in South Ecuador. We exclusively interpret terrain attributes, derived from a digital elevation model, as proxies to several driving factors of landslides and use them as predictors in our models which are trained on a set of five historical landslide inventories. We check the model generality by transferring them in time and use three common performance criteria (i.e. AUC, explained deviance and slope of model calibration curve) to, on the one hand, compare several state-of-the-art model approaches and on the other hand, to create weighted model ensembles. Our results suggest that it is important to consider more than one single performance criterion. Approaching our main question, we compare responses of weighted model ensembles that were trained on distinct functional units of landslides (i.e. initiation, transport and deposition zones). This way, we are able to show that it is quite possible to deduce driving factors of landslides, if the consistency between the training data and the processes is maintained. Opening the ?black box? of statistical models by interpreting univariate model response curves and relative importance of single predictors regarding their plausibility, we provide a means to verify this consistency. With the exception of classification tree analysis, all techniques performed comparably well in our case study while being outperformed by weighted model ensembles. Univariate response curves of models trained on distinct functional units of landslides exposed different shapes following our expectations. Our results indicate the occurrence of landslides to be mainly controlled by factors related to the general position along a slope (i.e. ridge, open slope or valley) while landslide initiation seems to be favored by small scale convexities on otherwise plain open slopes.

Abstract:

Shallow landslides are an important type of natural ecosystem disturbance in tropical montane forests. Due to landslides, vegetation and often also the upper soil layer are removed, and space for primary succession under altered environmental conditions is created. Little is known about how these altered conditions affect important aspects of forest recovery such as the establishment of new tree biomass and species composition. To address these questions we utilize a process-based forest simulation model and develop potential forest regrowth scenarios. We investigate how changes in different trees species characteristics influence forest recovery on landslide sites. The applied regrowth scenarios are: undisturbed regrowth (all tree species characteristics remain like in the undisturbed forest), reduced tree growth (induced by nutrient limitation), reduced tree establishment (due to thicket-forming vegetation and dispersal limitation) and increased tree mortality (due to post-landslide erosion and increased susceptibility). We then apply these scenarios to an evergreen tropical montane forest in southern Ecuador where landslides constitute a major source of natural disturbance. Our most important findings are (a) On the local scale of a single landslide tree biomass recovers within the first 80 years after landslides for most scenarios, but it takes at least 200 years for the post-landslide forest to reach a structure (in terms of stem size distribution) similar to a mature forest. On this scale forest productivity is reduced for most regrowth scenarios. Changes in different tree species characteristics produce distinct spatio-temporal patterns of tree biomass distribution in the first decades of recovery within the landslide disturbed area. These patterns can potentially be used for identifying the dominant processes that drive forest recovery on landslide disturbed sites. (b) On the larger scale of the landscape overall tree biomass is reduced by 9?15% due to landslide disturbances. Overall forest productivity is only slightly reduced (<6%), but landslides increase landscape heterogeneity and produce hotspots of biomass loss and ?blind spots? of forest productivity. Thus landslides have a strong impact on the distribution of biomass in tropical montane forests. This study demonstrates that dynamic forest models are useful tools for complementing field based studies on landslides; they allow for testing alternative hypotheses on different sources of heterogeneity across spatial scales and investigating the influence of landslides on long-term forest dynamics.

Abstract:

Understanding pasture degradation processes is the key for sustainable land management in the tropical mountain rainforest region of the South Ecuadorian Andes. We estimated the stocks of total carbon and nutrients, microbial biomass and different P fractions along a gradient of land-uses that is typical of the eastern escarpment of the Cordillera Real i.e., old-growth evergreen lower montane forest, active pastures (17 and 50 years-old), abandoned pastures 10 and 20 years old with bracken fern or successional vegetation. Conversion of forest to pasture by slashand- burn increased the stocks of SOC, TN, P and S in mineral topsoil of active pasture sites. Microbial growth in pasture soils was enhanced by improved availability of nutrients, C:N ratio, and increased soil pH. Up to 39 %of the total P in mineral soil was stored in the microbial biomass indicating its importance as a dynamic, easily available P reservoir at all sites. At a 17 years-old pasture the stock of NH4F extractable organic P, which is considered to be mineralisable in the short-term, was twice as high as in all other soils. The importance of the NaOH extractable organic Ppool increased with pasture age. Pasture degradation was accelerated by a decline of this P stock, which is essential for the long-term P supply. Stocks of microbial biomass, total N and S had returned to forest levels 10 years after pasture abandonment; soil pH and total P 20 years after growth of successional bush vegetation. Only the C:N ratio increased above forest level indicating an ongoing loss of N after 20 years. Soil nutrient depletion and microbial biomass decline enforced the degradation of pastures on the investigated Cambisol sites.

Abstract:

The World Reference Base for Soil Resources (WRB) (FAO, IUSS Working Group WRB, 2007) at present does not acknowledge the spatial soil continuum, but provides a sound basis to do so. Using methods from statistical learning theory to develop digital soil maps is much more efficient and precise while regionalising soil diagnostic properties instead of complex entities such as the soil units assigned by the WRB. Particularly in providing spatial soil information displayed in digital soil maps, any aggregation of this spatial soil information to soil units means a loss of information. The soil landscape can be systematically described in its spatial continuum simply by the vertical order and extent of the WRB diagnostic horizons. The diagnostic horizons are related in their thickness to a standard depth and listed from top to bottom in order of appearance. Typical diagnostic horizon thickness and occurrence probability were predicted from terrain parameters by classification and regression trees (CART), throughout the research area in southern Ecuador. The two disadvantages of CART, abrupt prediction class boundaries and dependence on the dataset, were addressed by hundredfold model runs on different data subsets, leading to a range of possible predictions. Prediction uncertainty was included in the digital soil maps by calculating these predictions' means and standard deviations as well as by horizon occurrence probability prediction. Model performance was evaluated by means of hundredfold external cross validation. Terrain parameters were found to have a strong influence on diagnostic topsoil properties. However, no influence on the vertical profile differentiation was observed. Hence predicting horizon thickness and subsoil diagnostic properties was difficult. The systematic description of the soil continuum of this particular soillandscape resulted in histic and stagnic soil parts dominating the first 100 cm of the soil column for most of the area.

Abstract:

The main objective of this dissertation was to identify the rainfall runoff processes that control the discharge generation of the study areas. The research uses multi techniques including hydrometric data analysis, tracers (isotopes and chemical constituents) and conceptual modeling. The research questions were (i) in which way streamflow is controlled by micro-climate, precipitation pattern, slope, land cover and soil properties, amongst other catchment properties?, (ii) what are the main sources of water within the study areas?, and how the soil properties are influencing the runoff generation?, and (iii) could the identified conceptual model, using previous knowledge, be applied for the studied areas in the south of Ecuador?

Abstract:

Parallel to the proceeding destruction of the megadiverse mountain forests of Ecuador more and more plantations with exotic Pinus and Eucalyptus species are being established. An ecologically reasonable reforestation could help to solve the problem. Such a reforestation can only be achieved by using indigenous species. As the harvest of seeds is problematic, plant material has to be produced by means of vegetative propagation. However, we have been lacking a knowledge base and efficient methods for cloning native tree species so far. ? In the present thesis the potential to vegetatively propagate as well as the carbohydrate and phytohormone content of the following six tree species ? naturally occurring in the mountain forests of Southern Ecuador ? were examined: Clethra revoluta (Clethraceae), Heliocarpus americanus (Tiliaceae), Isertia laevis (Rubiaceae), Myrica pubescens (Myriaceae), Piptocoma discolor (Asteraceae) and Tabebuia chrysantha (Bignoniaceae). ? Despite variegated variations of the propagation conditions over 1 ½ years we did not succeed in obtaining rooted stem cuttings of adult trees. The plants withered rapidly. Measurements of stomatal leaf conductance show an insufficient regulation of the stomata associated with high transpiration rates. Although the production of rooted stem cuttings of adult trees by air-layering was successful, these plants withered after placing them in soil, too. ? The carbohydrate measurements resulted in annual fluctuations in several species concerning their starch and soluble sugar content ? especially for the raffinose family (Tabebuia); an increased inositol content during the drier months could also be observed in all species. Although the total carbohydrate content showed clear seasonal fluctuations in the leaves (Heliocarpus-, Myrica and Tabebuia plants) no definite fluctuations could be detected in the twigs at all. Whereas Heliocarpus and Tabebuia trees stored reserve carbohydrates with a content of 6 or 9.5 %, respectively (especially in the form of starch as well as glucose, fructose and sucrose) the low carbohydrate supply in the twigs of Clethra and Piptocoma during the whole year could have been detrimental to successful adventive rooting. ? It is presumed that the endogenous content of cytokinins (initiation of root primordia) and auxins (root growth) is especially important for the rooting of cuttings. The measured phytohormone status fluctuates depending on season and species. A hormone status suitable for the root formation (= a high auxin : cytokinin ratio) was found in Heliocarpus and Tabebuia in the months with the highest precipitation rates. On the contrary Clethra and Myrica contained hardly any auxin but relatively much cytokinin. Thus rooting seems to be especially difficult with these species. ? As it is not possible to interfere in the hormone status of adult trees, young plants were used as donor plants for their hormone and metabolic reserve status can be changed adequately by stressing treatments. We especially aimed at lowering the cytokinin level endogenously. For these experiments Heliocarpus and Tabebuia were selected and exposed to shortage of water, nutrients or root space as well as combinations of these stress factors. Additionally wildlings (saplings) were used. ? This strategy turned out to be successful because from all treatments 42 % of the Heliocarpus and 15 % of the Tabebuia cuttings rooted on average. The most successful cuttings originated from Heliocarpus treelets exposed to water shortage (70 % rooting) and from Tabebuia plants exposed to nutrient shortage (15 %). Wildlings of Tabebuia also grew roots effectively (45 %). Even better results in the two species were achieved by air-layering. ? The pretreatments resulted in an increase of the carbohydrate content (except for Tabebuia plants under water shortage). However, no statistically significant correlation aroused between the carbohydrate content of the differently stressed donor plants and the rooting percentage. ? As assumed the stressful pretreatment of the donor plants of both species caused a lower cytokinin level whereas at least in Tabebuia a significantly negative correlation between the rooting of cuttings and the cytokinin content of the donor plants was found (rs up to -0.93). ? The results of this thesis clearly show that even young twigs of adult tropical trees have virtually no rooting potential. In young plants this potential can be activated by stress whereas the accumulation of metabolic reserves and the decrease of the cytokinin level had a beneficial influence on the rooting percentage. This constellation was rather developed in Tabebuia than in Heliocarpus. ? Due to the possibility of making at least two cuttings from one donor plant the establishment of a cultivation of cloned material for reforestation is ? although time-consuming ? definitely feasible.

Abstract:

We investigated the role of carbon, nitrogen and phosphorus as limiting factors of microorganisms and microbial grazers (testate amoebae) in a montane tropical rain forest in southern Ecuador. Carbon (as glucose), nitrogen (as NH4NO3) and phosphorus (as NaH2PO4) were added separately and in combination bimonthly to experimental plots for 20 months. By adding glucose and nutrients we expected to increase the growth of microorganisms as the major food resource of testate amoebae. Th e response of microorganisms to experimental treatments was determined by analysing microbial biomass (SIR), fungal biomass and microbial community composition as measured by phospholipid fatty acids (PLFAs). We hypothesized that the response of testate amoebae is closely linked to that of microorganisms. Carbon addition strongly increased ergosterol concentration and, less pronounced, the amount of linoleic acid as fungal biomarker, suggesting that saprotrophic fungi are limited by carbon. Microbial biomass and ergosterol concentrations reached a maximum in the combined treatment with C, N and P indicating that both N and P also were in short supply. In contrast to saprotrophic fungi and microorganisms in total, testate amoebae suff ered from the addition of C and reached maximum density by the addition of N. Th e results indicate that saprotrophic fungi in tropical montane rain forests are mainly limited by carbon whereas gram positive and negative bacteria benefi t from increased availability of P. Testate amoebae suff ered from increased dominance of saprotrophic fungi in glucose treatments but benefi ted from increased supply of N. Th e results show that testate amoebae of tropical montane rain forests are controlled by bottom?up forces relying on specifi c food resources rather than the amount of bacterial biomass with saprotrophic fungi functioning as major antagonists. Compared to temperate systems microbial food webs in tropical forests therefore may be much more complex than previously assumed with trophic links being rather specifi c and antagonistic interactions overriding trophic interactions.

Abstract:

We investigated changes in diversity and density of testate amoebae in epiphytes of trees in tropical montane rain forests of southern Ecuador. Local ? microscale [height on tree trunk of 0 (base of tree trunk), 1 and 2 m; TH I, TH II and TH III, respectively] and regional ? macroscale (forests at 1000, 2000 and 3000 m) changes were investigated. At the macroscale diversity and density of testate amoebae peaked at 2000 m. At the microscale diversity reached a maximum at TH I, whereas density reached a maximum at TH III. The percentage of empty shells at the macroscale was at a maximum at 2000 m and at the microscale at TH I, whereas the percentage of live cells was at a maximum at 3000 m and at TH III. The diversity of testate amoebae in epiphytes found in the present study was high (113 species). However, only two to nine species were dominant representing 54?85 percent of total living testate amoebae. The results suggest significant variations in density and diversity of testate amoebae at both the micro- and macroscale. However, for testate amoebae density the macroscale appears most important whereas changes in diversity are more pronounced at the microscale.

Abstract:

Litter quality and diversity are major factors structuring decomposer communities. However, little is known on the relationship between litter quality and the community structure of soil protists in tropical forests. We analyzed the diversity, density, and community structure of a major group of soil protists of tropical montane rainforests, that is, testate amoebae. Litterbags containing pure and mixed litter of two abundant tree species at the study sites (Graffenrieda emarginata and Purdiaea nutans) differing in nitrogen concentrations were exposed in the field for 12 months. The density and diversity of testate amoebae were higher in the nitrogen-rich Graffenrieda litter suggesting that nitrogen functions as an important driving factor for soil protist communities. No additive effects of litter mixing were found, rather density of testate amoebae was reduced in litter mixtures as compared to litterbags with Graffenrieda litter only. However, adding of high-quality litter to low-quality litter markedly improved habitat quality, as evaluated by the increase in diversity and density of testate amoebae. The results suggest that local factors, such as litter quality, function as major forces shaping the structure and density of decomposer microfauna that likely feed back to decomposition processes.

Abstract:

The tropical Andes in southern Ecuador constitute a hotspot of plant (especially trees and bryophytes) and animal (especially birds, bats, arctiid and geometrid mothes) diversity. However, data on small animals such as testate amoebae as an important component of the soil and aboveground community are lacking. Variations in density, diversity and community structure of testate amoebae along altitudinal transects in tropical regions are largely unknown. Testate amoebae colonize almost any habitat but are most abundant and diverse in soils with high humidity, high organic content and slow rates of decomposition. They preferentially feed on certain bacteria thereby affecting the taxonomic composition and metabolic activity of microbial communities. By altering microbial activity testate amoebae affect nutrient cycling in particular in ecosystems where earthworm populations are depleted. The present thesis investigates the density and diversity of testate amoebae in litter, soil and aboveground habitats along an elevational gradient of tropical mountain rain forests in southern Ecuador, evaluates correlations with biotic and abiotic factors, and proves the role of nutrient limitation.

Abstract:

Global biodiversity is threatened by climate and land cover change. The research unit "Biodiversity and Sustainable Management of a Megadiverse Mountain Ecosystem in South Ecuador" (FOR 816) funded by the German research council (Deutsche Forschungsgemeinschaft, DFG) is working in one of the hottest hotspots of biodiversity of the world. In this region the pressure from the local population on the environment is severe resulting in a high deforestation rate. Sustainable management systems have to be developed on a regional scale to counteract the loss of livelihood of the local population. Numerical models are capable to investigate the changes of the mentioned future land cover changes and its response to climatic and hydrologic variability. The chance to test numerously land use scenarios without interfering into the real environment offers the possibility to investigate and to evaluate the proposed management strategies. The presented work targets at an analysis of the impact of the predicted land cover changes in respect of the ecosystem services of climate and water regulation. Therefore a state-of-the-art land surface model called "Community Land Model" (CLM) is setup in a regional scale. The parametrization of the vegetation is implemented using plant functional types (PFT). The PFTs are defined a priori with vegetation classes based on ecological field surveys. Three central hypotheses are formulated to support the parametrization of the model. The completed work offers a regionalized model setup to analyze different land cover developments in reference to energy and water fluxes between the soil, the vegetation and the atmosphere under changing climatic conditions. Besides the appraisal of the stated hypotheses other innovative contributions are made. The new values for the pre-installed CLM-PFT of tropical evergreen trees add to the current improvements made to the CLM.